In the radio transceiver employing the WCDMA system or the like, a duplexer separates transmission from reception and thus it is common to simultaneously perform wireless transmission and reception through an antenna. In such a radio transceiver, transmission signals are leaked into a receiving circuit through the duplexer, so that reception performance would be deteriorated.
Therefore, the duplexer is typically designed so as to reduce the influence of the transmission signals on the reception performance, by sufficiently ensuring its isolation characteristic between transmission and reception.
Further, it is also common that the duplexer has a differential connection with the receiving circuit for the purpose of accurately propagating reception signals. In this case, two signals (a pair of differential signals) are input to the receiving circuit. Thus, interference occurs within a reception bandwidth due to inter modulation, and thereby causes the deterioration of the reception performance.
Therefore, the receiving circuit is often provided with functions for reducing the interference due to the inter modulation. For example, PTL 1 discloses a radio transceiver in which current control is performed for an LNA (Low Noise Amplifier) and a mixer in a receiving circuit in order to reduce interference caused by inter modulation when transmission signals are leaked.